钾泡弥散与钨丝性能

自从美国A.Pac’z制造出不下垂钨丝至今已有70年的历史了,但是,这种抗下垂钨丝,即所谓的掺杂钨丝,具有如此优良的高温强度的本质,却是六十年代末七十年代初电子显微镜应用于钨科学研究中才开始揭示出来的。均匀细小弥散的钾泡是掺杂钨丝得以强化的关键因素。人们对钾泡的形成及其作用进行了大量的研究工作,并且,这种研     

垂熔制度对掺杂钨性能的影响

烧结的目的是通过高温作用得到接近理论密度和无孔隙的制品。而在掺杂钨中，需要形成合适的钾泡来稳定细微孔隙，以使钨丝具有高温蠕变强度；同时需去除钨中的杂质和无效掺杂剂。本文的研究表明，通过合理的垂熔烧结制度可使钨条密度最佳。     

第一次还原温度对掺杂钨丝高温抗蠕变性能的影响及其机制的探讨

第一次还原温度对掺杂钨丝的高温抗蠕变性能有显著影响。钨丝抗蠕变性能与其钾含量密切相关,而钾含量主要取决于掺杂效应和掺杂机制。当掺杂机制以β-w至α-w相变为主时,垂熔过程中K残留60～70wt.％;当掺杂机制以颗粒长大为主时,K只能残留30～40wt.％。成串排列的掺杂泡阻碍再結晶过程中钨晶界的横向运动。     

耐震钨丝特性及应用

研究了高钾掺杂钨丝、加钴掺杂钨丝和加铼掺杂钨丝的高温特性和耐震性能 ,进行了应用试验 ,指出了生产耐震灯泡时选用钨丝应注意的问题。     

掺杂钨丝的再结晶动力学

本文比较系统地研究了不同丝径掺杂钨丝的再结晶速度及其影响因素。结果表明,低温区,形变量越大,完成再结晶所需退火时间越短,符合经典的再结晶规律;但在高温区则相反。笔者认为,掺杂钨丝高温区再结晶动力学的反常是由于高度密排的钾泡列阻碍了晶界横向迁移所致。     

抗下垂掺杂钨中钾泡的形成及其作用

<正> 本文描述了在抗下垂掺杂钨坯烧结过程中钾泡的形成、热加工过程中钾泡的形态变化及其在灯丝中的作用,并初步探讨了烧结过程中坯条化学成分的变化和钨粉还原的致密化动力学。 烧结的抗下垂掺杂钨坯的主要特征是含抗下垂掺杂剂的还原钨粉料制成的钨坯基体的亚微孔洞中形成钾泡。与钾泡形成有关的化学变化(如钾的密度、钾泡的分布、晶粒结构和密度)对坯条性能及最终的白炽灯丝性能是至关重要的。本文结合主要烧结机理对1200～1300℃温度区间内抗下垂掺杂钨坯的     

逆氢蓝钨工艺对掺杂钨丝高温性能的影响

不同相成分的蓝钨对掺杂钨丝的高温性能有显著影响。在采用通氢还原法制备蓝钨工艺中，通过研究顺氢和逆氢两种工艺下的蓝钨相成分及以此为原料生产的掺杂钨丝高温性能，对比不同预还原工艺下生产丝材的再结晶组织以及所加工的掺杂钨丝高温性能的差异，探讨逆氢还原气氛所生产的蓝钨对掺杂钨丝高温性能的强化机理。结果表明，采用逆氢还原法能有效提高铵钨青铜成分，所生产的掺杂钨丝高温抗下垂性能得到显著提升。     

试述影响掺杂钨条密度的因素及其生产控制

<正> 掺杂钨条的密度对于制作灯泡用钨丝的生产具有至关重要的作用,因此获取适宜密度的掺杂钨条,对于生产具有必要的强度、延性、韧性和抗下垂性等综合性能优异的钨丝是有重要意义的。下面将生产过程中影响掺杂钨条密度的几个主要因素略述如下:一、掺杂元素的影响我厂生产的灯泡用钨丝的各项性能是通过在 WO_3中掺杂少量的硅、铝、钾的化合物来达到的。实践证明:硅和铝在烧结时几     

液—固掺杂垂熔钨坯中改性元素的行为

对传统粉末冶金方法(液—固混合制成掺杂钨粉,经过压制、烧结、旋锻、拉拔等工序)制成的钨坯和钨丝,用扫描电子显微镜进行了断面及磨面分析。结果发现:在晶界孔穴内,元素Si和Al的含量丰富;在晶内孔穴内,除元素Si、Al外,还富集了元素K。只用钾泡理论解释改性元素改善高温钨丝的抗下垂性能是不够的,应以分子筛理论和SiO_2-Al_2O_3系统相图予以补充。     

GHM钼气孔弥散与机械性能的关系研究

本文通过扫描电镜,俄歇谱仪和金相显微镜等手段,对掺杂钼和纯钼的粉,条乃至丝材,进行横、纵向观察,其结果表明,掺杂钼丝的再结晶温度比纯钼丝高,在1800℃以上仍保持着良好的机械性能。文章初步探讨了高温退火处理后,仍具有良好机械性能的机制。研究表明:掺杂钼丝经高温退火后,晶粒表面形成了规则排列的钾泡,阻碍了掺杂钼丝再结晶晶粒的横向长大。使晶粒沿丝轴方向和无钾泡处生长,形成锯齿形长晶,这种晶粒间相互啮合搭接,导致了高温退火后的掺杂钼丝具有良好的塑性和弯曲性能;并且钾泡行密度和长度愈大,则再结晶晶形比值L/W(L为再结晶晶粒长度,W为宽度)愈大,其机械性能也愈好。     

A Model for the formation of the non-sag structure of potassium-doped tungsten wire

During recrystallization, potassium-doped tungsten wire develops a favorable stable structure of elongated grains. This is caused by a special bubble structure which is produced by the doping agent, potassium. The paper aims at a coherent semiquantitative model describing the formation of sinter pores, of potassium bands during deformation, of the bubble structure, and of driving and dragging forces during recrystallization.     

The effect of wire history on the coarsened substructure and secondary recrystallization of doped tungsten

This article reports a study of primary and secondary recrystallization in tungsten wire. Samples with two different processing histories were annealed in the electron emission microscope, and the recrystallization process was followed. The fibers produced by drawing were first observed to widen and break up into shorter lengths. As the temperature was raised, the secondary recrystallization occurred in a characteristic, stepwise motion, with the secondary grain moving from one position to the next and then remaining pinned at the new position, sometimes for the entire length of the test. It was found that the temperature at which secondary recrystallization occurred depended on the heating rate. If a slow heating rate was used, the temperature at which secondary recrystallization occurred would be higher. This result was interpreted to mean that the slower heating rate allowed more strain to be annealed out of the wire before secondary recrystallization occurred and thus lowered the driving force for this process. The secondary recrystallization temperature could not be correlated with the primary grain structure or differences in the potassium bubble distribution in the wire. The primary recrystallized grain structures of the two wires were also different, and this difference, too, was attributed to differences in the amount of stored energy in the wire at the start of the annealing. It was also shown that even though the bulk potassium content of the two wires was the same and the bubble distributions in the two wires were similar, the bubble distributions in the ingots were different.     

Measurement of bubble characteristics in a molten iron bath at 1600 °C using an electroresistivity probe

A two-needle, electroresistivity probe was developed to measure bubble characteristics such as gas holdup, bubble frequency, and bubble rising velocity in a molten iron bath at 1600 °C. The probe’s electrode was made of a 0.5-mm platinum wire coated with ZrO₂ cement and an outer coat of alumina as insulator. The life of this probe at 1600 °C was 15 to 20 minutes, making it possible to systematically measure bubble characteristics. The measured values of the bubble characteristics were compared with their respective empirical correlations derived from cold model experiments. Good agreement between the measured values and the empirical correlations was seen for each bubble characteristic. This electroresistivity probe allows us to measure bubble characteristics in actual metallurgical reactors with gas injection at high bath temperatures.     

Investigation on Bodily Fault in Doped W Wire by Electronic Miscroscope

Ithasarousedmoreandmoreattentionthatsomepuremetalsaddedbydopitiveorneutronbombardmentleadinonekindofbodilyfaulttoincreasematerialstrengthathightemperature[1,2].Especially,afewadditivesuchasSi,Al,KareaddedtomakeundroopWwire.Mostofthesedopedthingshavebeenvolatilizedintheprocessofsintering,andtheremainderesformabodilyfault(Kbubbleswitheveragediameterof20nm)inthefollowingworkingprocess.ThedenseKbubbleshinderedthemovementofgrainboundaryintheheatingprocess,andheightenedthepropertiesagainstdroopof…     

The recrystallization of commercially pure and doped tungsten wire drawn to high strain

The recrystallization processes in both undoped and doped tungsten wire after drawing to a true strain of 7.7 were examined by light microscopy and transmission electron microscopy. High angle grain boundary migration commenced at approximately the same temperature in both materials, but proceeded much more rapidly in the undoped wire, where the absence of a potassium bubble dispersion allowed a coarser, more equiaxed grain structure to form. No change from the (110) deformation texture was observed in either case. Recrystallization in the undoped wire was dominated at lower temperatures (1100 to 1200°C) by the growth of large grains into a much finer structure. As the annealing temperature was increased, this process was replaced by a general grain coarsening which eventually produced a relatively equiaxed recrystallized grain structure. It appeared probable that it was the second phase dispersion inhibition alone that prevented similar structural changes in the doped wire. This paper is based on a presentation made at a symposium on “Recovery Recrystallization and Grain Growth in Materials” held at the Chicago meeting of The Metallurgical Society of AIME, October 1977, under the sponsorship of the Physical Metallurgy Committee.     

Recrystallization of molybdenum wire doped with potassium-silicate

The doping effect of the bubble formation oxide on the recrystallization of Mo wire was investigated. Five different wires of 1 mm in diameter were prepared through sintering, swaging, and drawing processes. Each wire was doped with various amounts of potassium (K) plus silicon (Si), i.e., 0, 0.028, 0.14, 0.28, and 0.49 by weight percent, and annealed for 30 minutes at given temperatures. To understand the overall recrystallization phenomena, changes in hardness and in optical microstructures were examined. Transmission electron micrographs were taken for the specimens in the as-drawn state and at the beginning of the decrease in hardness. And also, the relative excess resistivity was measured as a function of heating temperature to confirm the occurrence of the abnormal grain growth. During the grain growth, bubble dispersion was evaluated through fractography by scanning electron microscopy (SEM). Primary re-crystallization started at 750 °C regardless of the amount of dopants. For the specimens doped with 0.14 and 0.28 (K + Si), large elongated and interwoven grain structures indicating ab-normal grain growth developed over 1400 °C and 1600 °C, respectively. For the specimens doped with 0.028 and 0.49 (K + Si), however, small equiaxial grain structure developed similar to pure molybdenum wire. Such a difference was understood through the relationship between grain structures and bubble dispersion parameters (the average bubble diameter, the bubble row density, the columnar bubble spacing, and the bubble row distance). It was concluded that two of the most important parameters to develop a grain structure of high aspect ratio were bubble row density and bubble row distance. At a high bubble row density, irregularity in bubble row distance induced the higher aspect ratio (length/width (L/W)) of grain.     

SEM在安钢线材研发中的应用

简要介绍了扫描电子显微镜(SEM)的工作原理。结合安钢线材研发实际情况,利用SEM分析了冷镦钢表面裂纹形貌、形成机理及高碳盘条82B常见的拉拔断裂断口形貌、形成原因等,对优化生产工艺、提高产品实物质量具有重要意义。     

气体旋流喂丝枪喂椭圆包芯线实现钢液内部喂丝钙处理

介绍了钢包中钢液钙处理的起源及钙的加入方法和研制的气体旋流喂丝枪和高致密椭圆截面包芯线。建议包芯线成形机和喂丝机生产企业借鉴焊管成形机进行技术改造,生产椭圆截面包芯线成形机;将圆拄面齿形喂丝轮改造成圆弧槽喂丝轮;钢铁企业喂丝处理时增加活动导丝管升程,以实现钢液内部喂丝钙处理。     

Heat transfer performance of porous titanium

Porous titanium fibre materials with different structural parameters were prepared by vacuum sintering method. The thickness,porosity and wire diameter of prepared materials were investigated to understand the effects of structural parameters on pool heat transmission performance of titanium fibre porous material. As a result,better heat transfer performance is obtained when overheating is less than 10 °C. In addition,when the wire diameter is smaller,the heat transfer is better. However,when superheating is above 10 °C,heat transfer performance can be improved by increasing the wire diameter. Moreover,thickness influences the superficial area of the prepared material and affects the thermal resistance when bubbles move inside the material; superficial area and thermal resistance are the two key factors that jointly impact the heat transfer in relation to the thickness of the materials. Experimental results also show that the materials of 3 mm in thickness exhibit the best performance for heat transmission. Furthermore,changes in porosity affect the nucleation site density and the resistance to bubble detachment; however,the nucleation site density and the resistance to bubble detachment conflict with each other. In summary,the titanium fibre porous material with a 50% porosity exhibits suitable heat transfer performance.     

Prediction of Bubble Size Distribution in Aluminium Foam as a Function of %Titanium Hydride Addition

Foaming of liquid aluminium by addition of foaming agent (TiH₂ particles) is numerically simulated using population balance equations. Phenomena such as hydrogen release by the TiH₂ particles, heterogeneous nucleation of bubbles in oxide surface cavities, and diffusion based bubble growth are modelled. A simple mass transfer coefficient, which varies inversely with the bubble size is used to estimate the bubble growth rate. Simulation is performed to study the effect of TiH₂ content on the final bubble size distribution, total number of bubbles and average bubble size. In general, the average properties of the predicted distributions are close to the experimental values, whereas the spread in the bubble size is observed to be considerably narrower for the predicted values. The deviation in the spread of the distributions is attributed to the inverse bubble size dependent growth rate and non-inclusion of bubble coalescence in the model.